1. Technical Field
The present invention relates to a shearing die for shearing a sheet or plate material, and a method for manufacturing the shearing die.
2. Background Art
With an increase in strength of metal materials such as high-tensile steel products, the shortened life of shearing dies used for shearing of sheet or plate materials composed of the metal materials have become a problem. Accordingly, in order to solve this problem, techniques of forming various hard films as described below on substrates of the dies have now been created.
For example, Patent Document 1 discloses a technique of forming a ceramic of any one of carbides, nitrides and carbonitrides of the group IV elements on a substrate surface of a shearing flat-blade knife. Further, Patent Document 2 discloses a technique of forming a ceramic of a titanium nitride as an inner layer, a titanium metal layer as an intermediate layer and a ceramic of a titanium nitride as an outer layer on a substrate surface of a shearing flat-blade knife.
Furthermore, Patent Document 3 discloses a method for manufacturing a die for punch press, in which after heat treatment, cutting, electric discharge working and the like are performed to a substrate of the die, a nitride layer is formed by ion nitriding on a cutting blade part of the die or a contact part of the die with a sheet or plate material, and thereafter ion plating is performed with titanium evaporating particles, thereby forming a film of a nitride, carbide or carbonitride of titanium on a surface part of the die.
It has been conceivable herein that the main causes for damage of a shearing die are fatigue fracture of the die caused by repeated application of impact and wear of a cutting blade part of the die caused by friction with a sheared sheet or plate material. Accordingly, the damage of the shearing die can be decreased to some degree by applying the hard films having high hardness disclosed in Patent Documents 1 to 3 to the shearing die.    Patent Document 1: JP-A-8-325706    Patent Document 2: JP-A-8-325707    Patent Document 3: JP-A-2000-343151